Additive manufacturing method for the addition of features within cooling holes

ABSTRACT

A method for forming a diffusion cooling hole in a substrate includes removing material from the substrate to form a metering section having an inlet on a first side of the substrate and removing material from the substrate to form a diffusing section that extends between the metering section and an outlet located on a second side of the substrate generally opposite the first side. The method also includes forming a feature on a substrate surface within one of the metering section and the diffusing section. Forming the feature includes depositing a material on the substrate surface and selectively heating the material to join the material with the substrate surface and form the feature.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.14/771,436, filed Aug. 28, 2015, for “ADDITIVE MANUFACTURING METHOD FORTHE ADDITION OF FEATURES WITHIN COOLING HOLES”, by JinQuan Xu, which isa 371 of PCT Application No. PCT/US2014/023393, filed Mar. 11, 2014, for“ADDITIVE MANUFACTURING METHOD FOR THE ADDITION OF FEATURES WITHINCOOLING HOLES” by JinQuan Xu, which in turn claims the benefit of U.S.Provisional Application No. 61/790,122, filed Mar. 15, 2013, for“ADDITIVE MANUFACTURING METHOD FOR THE ADDITION OF FEATURES WITHINCOOLING HOLES” by JinQuan Xu.

BACKGROUND

This invention relates generally to turbomachinery, and specifically toturbine flow path components for gas turbine engines. In particular, theinvention relates to cooling techniques for airfoils and other gasturbine engine components exposed to hot working fluid flow, including,but not limited to, rotor blades and stator vanes, platforms, bladeouter air seals (BOAS), shrouds and compressor and turbine casings,combustor liners, turbine exhaust assemblies, thrust augmentors andexhaust nozzles.

Gas turbine engine performance depends on the balance between pressureratios and core gas path temperatures and the related effects on servicelife and reliability due to stress and wear. This balance isparticularly relevant to gas turbine engine components in thecompressor, combustor, turbine and exhaust sections, where activecooling may be required to prevent damage due to high gas pathtemperatures.

SUMMARY

A method for forming a diffusion cooling hole in a substrate includesremoving material from the substrate to form a metering section havingan inlet on a first side of the substrate and removing material from thesubstrate to form a diffusing section that extends between the meteringsection and an outlet located on a second side of the substrategenerally opposite the first side. The method also includes forming afeature on a substrate surface within one of the metering section andthe diffusing section. Forming the feature includes depositing amaterial on the substrate surface and selectively heating the materialto join the material with the substrate surface and form the feature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a wall having diffusion cooling holes.

FIG. 2 is a sectional view of the diffusion cooling hole of FIG. 1 takenalong the line 2-2.

FIG. 3 is a perspective view of a diffusion cooling hole before raisedfeatures have been added.

FIG. 4 is a perspective view of one embodiment of a diffusion coolinghole with features formed by additive manufacturing.

FIG. 5A is a cross section view of another embodiment of a diffusioncooling hole with features formed by additive manufacturing.

FIG. 5B is a cross section view of the diffusion cooling hole of FIG. 5Ataken along the line B-B.

FIG. 6 is a perspective view of another embodiment of a diffusioncooling hole with features formed by additive manufacturing.

DETAILED DESCRIPTION

FIG. 1 illustrates a view of a wall with cooling holes formed accordingto one embodiment of the present invention. Wall 10 is primarilymetallic and includes opposite surfaces 12 and 14. One or both ofsurfaces 12 and 14 can include a coating layer such as a thermal barriercoating. Cooling holes 16 are oriented so that their inlets 18 arepositioned along surface 12 of wall 10 and their outlets 20 arepositioned along surface 14 of wall 10. During gas turbine engineoperation, surface 14 is in proximity to high temperature gases (e.g.,combustion gases, hot air). Cooling air is delivered along surface 12 ofwall 10 where it enters inlets 18 of cooling holes 16, exits outlets 20of cooling holes 16 and forms a cooling film on surface 14. A variety ofcomponents that require cooling can include cooling holes 16. Suitablecomponents include, but are not limited to, turbine vanes and blades,combustors, blade outer air seals, and augmentors, etc. Cooling holes 16can be utilized on the pressure side or suction side of vanes andblades. Cooling holes 16 can also be utilized on the blade tip or bladeor vane platforms.

FIG. 2 illustrates a sectional view of cooling hole 16 of FIG. 1 takenalong the line 2-2. For the sake of comparison to later Figures, FIG. 2illustrates cooling hole 16 before the fine features are formed alongthe surfaces that define cooling hole 16. Cooling hole 16 includes inlet18, outlet 20, metering section 22 and diffusing section 24. Inlet 18 isan opening located on surface 12. Cooling air C enters cooling hole 16through inlet 18 and passes through metering section 22 and diffusingsection 24 before exiting cooling hole 16 at outlet 20 along surface 14.

Metering section 22 is adjacent to and downstream from inlet 18 andcontrols (meters) the flow of air through cooling hole 16. As shown inFIGS. 2 and 3, metering section 22 is defined by continuous, generallycircular surface 26. In some embodiments, metering section 22 has asubstantially constant flow area generally from inlet 18 to diffusingsection 24. Metering section 22 can have circular, oblong (oval orelliptical), racetrack (oval with two parallel sides having straightportions), crescent, cusp or dual-cusp shaped cross sections. In someembodiments, metering section 22 is inclined between surfaces 12 and 14of wall 10 as illustrated in FIG. 2 (i.e. metering section 22 is notperpendicular to wall 10). Axis 27 extends through the center ofmetering section 22 as shown in FIG. 2.

Diffusing section 24 is adjacent to and downstream from metering section22. As shown in FIGS. 2 and 3, diffusing section 24 is defined by bottomsurface 28, side surfaces 30 and 32 and top surface 34. As shown in FIG.2, diffusing section 24 diverges longitudinally from axis 27 andmetering section 22. Bottom surface 28 diverges longitudinally from axis27 as it extends from surface 26 to outlet 20. As best shown in FIG. 3,diffusing section 24 also diverges laterally from metering section 22.Side surfaces 30 and 32 flare out as they extend from surface 26 tooutlet 20. Cooling fluid traveling through cooling hole 16 diffuses andexpands to fill diffusing section 24.

FIG. 3 is a perspective view of cooling hole 16 before the fine featuresare formed along one or more of the surfaces that define the coolinghole. Surfaces 12 and 14 of wall 10 are not shown in FIG. 3 so that thefeatures of the cooling hole can be better illustrated. As shown in FIG.3, bottom surface 28, side surfaces 30 and 32 and top surface 34 definediffusing section 24, and extend from surface 26 to outlet 20.

Cooling holes 16 shown in FIGS. 2 and 3 are typically formed bytraditional manufacturing techniques in which material is removed fromwall 10 to form surfaces 26, 28, 30, 32 and 34 that define cooling hole16. Suitable methods of material removal include, but are not limitedto, drilling, laser drilling, machining, electrical discharge machining(EDM) and combinations thereof. For example, metering section 22 ofcooling hole 16 can be formed by drilling while diffusing section 24 ofcooling hole 16 is formed by EDM. In some cases, cooling hole 16 canalso be made using casting processes.

FIG. 4 illustrates one embodiment of a cooling hole with fine features.FIG. 4 is a perspective view of cooling hole 16 having raised feature 36on bottom surface 28. Raised feature 36 is formed within cooling hole 16by adding material to bottom surface 28. In this embodiment, feature 36is a raised region of material located on bottom surface 28. Unlikemetering section 22 and diffusing section 24, raised feature 36 cannotbe easily formed by removing material from wall 10. Casting, drilling,laser drilling, machining and EDM techniques cannot typically form thegeometry of raised feature 36 reliably and reproducibly orinexpensively. According to embodiments of the present invention, raisedfeature 36 is formed using additive manufacturing techniques.

Suitable additive manufacturing techniques for forming raised feature 36include, but are not limited to, selective laser melting, direct metallaser sintering, selective laser sintering and electron beam melting.The additive manufacturing technique chosen can depend on the type ofmaterial used to form raised feature 36. In some embodiments, raisedfeature 36 is formed of a metal, alloy or superalloy. In theseembodiments, any of the aforementioned techniques can be suitable. Inother embodiments, raised feature 36 is formed of a ceramic material. Inthese embodiments, selective laser sintering is typically used to formceramic raised feature 36. Each of these techniques involves heating athin layer of material and melting it so that it joins with a substrate.The heating/melting and joining process can be repeated several timesuntil the material has formed the desired raised feature 36.

More particularly, raised feature 36 is formed within cooling hole 16 bydepositing a material on bottom surface 28 and selectively heating thematerial so that it melts and joins with bottom surface 28 followingsolidification. This process is repeated until the desired featuregeometry and thickness has been formed. Joining the material with bottomsurface 28 forms raised feature 36 as shown in FIG. 4. Depending on thetype of material used to form raised feature 36 (e.g., alloy, ceramic,etc.), different deposition methods can be used. The material applied tobottom surface 28 can be a metal or ceramic powder that is sprayed orplaced on bottom surface 28. Alternatively, thin layers of metal can besequentially positioned along bottom surface 28 prior to each heatingstep. Metals and ceramic raw materials may also be formed into a slurryand brushed onto bottom surface 28.

Once a layer of material has been deposited on bottom surface 28, thematerial is selectively heated above it melting temperature so that itfuses and joins with bottom surface 28. The material is heated using ahigh powered laser or electron beam to deliver the energy necessary tomelt the material. In some embodiments where an electron beam is used toheat the material, the entire part can be placed within a vacuum. Wherethe first “layer” of material is applied to bottom surface 28 (i.e. thesubstrate), the laser or electron beam energy may also melt part ofbottom surface 28 in some cases, forming a strong bond between bottomsurface 28 and raised feature 36. After the melted material hassolidified, additional material is deposited and the heating process iscarried out again. This series of steps (depositing, heating/melting,solidifying) is repeated until raised feature 36 contains the desiredthree-dimensional shape and thickness.

Prior to formation, the desired geometric characteristics of raisedfeature 36 are determined. These characteristics generally include theshape, thicknesses, curvature and other three-dimensional qualities ofthe desired feature. Once these features have been determined, acomputer generates a computer-aided design (CAD) file, additivemanufacturing file format (AMF) file or other type of file that providesinstructions to control the additive manufacturing operation. This filecontains information that controls the layer-by-layer depositing andmelting process described above. In some embodiments, an additivemanufacturing machine or system deposits the material within coolinghole 16 and selectively melts the material to form raised feature 36.

In cooling hole 16 shown in FIG. 4, raised feature 36 is a pyramid-likethree dimensional structure. As noted above, a CAD, AMF or other filedescribing the geometry of raised feature 36 is generated by a computer.This file is used to control the layer-by-layer additive manufacturingprocess for creating raised feature 36. Raised feature 36 includes apex38 and four relatively planar surfaces extending from apex 38 to bottomsurface 28. Raised feature 36 diverts cooling air to the lateral edgesof diffusing section 24, lobes 40 and 42 as shown and described ingreater detail in FIG. 8 and the accompanying description in U.S. patentapplication Ser. No. 13/544,090, filed on Jul. 9, 2012 and entitled“Multi-lobed cooling hole”.

While the formation of raised feature 36 on bottom surface 28 has beendescribed, raised feature 36 can be similarly formed on side surfaces 30and 32 and top surface 34 or on surface 26. Raised feature 36 can alsobe flat or curved as necessary to divert cooling air through coolinghole 16.

Additive manufacturing techniques can also be used to form other typesof raised features, such as cusps in the metering section of a coolinghole. FIGS. 5A and 5B illustrate cross section views of a cooling holeand one example of raised feature 36A formed within metering section 22of cooling hole 16A. As shown in FIG. 5A, raised feature 36A is formednear the downstream end of metering section 22 on surface 26. Raisedfeature 36A obstructs a portion of metering section 22 and creates acusp-like opening as shown in FIG. 5B. Raised feature 36A obscures aline of sight between inlet 18 and outlet 20 of cooling hole 16A. Raisedfeature 36A cannot be easily formed by drilling or EDM methods. Thus,raised feature 36A is formed according to the additive manufacturingmethods described above with respect to FIG. 4.

FIG. 6 illustrates another embodiment of a cooling hole having raisedfeatures formed by additive manufacturing techniques. FIG. 6 is aperspective view of cooling hole 16B having raised features 36B alongall the surfaces that extend from metering section 22 to the outlet 24A(bottom surface 28, side surfaces 30 and 32 and top surface 34). Coolinghole 16B appears similar to cooling hole 16 shown in FIG. 4. The dashedlines near outlet 20A illustrate the location of outlet 20 in FIG. 4. Inthis embodiment, additional material has been added to bottom surface28, side surfaces 30 and 32 and top surface 34 along and near outlet 20Ato provide a cooling hole with “sharper corners”. As noted above, a CAD,AMF or other file describing the geometry of raised feature 36B (thedifference in distance between outlet 20 and outlet 20A) is generated bya computer. This file is used to control the layer-by-layer additivemanufacturing process for creating raised feature 36B that reduces thesharp corners of outlet 20.

Wide corners reduce the thermal mechanical fatigue of wall 10 whilesharp corners reduce the likelihood of flow separation of cooling airexiting diffusing section 24, thereby improving cooling effectiveness.Cooling holes can be fine tuned to contain wide corners, sharp corners,or a combination of both wide and sharp corners along the outlet to fitthe specific needs based on the cooling hole location. As shown in FIG.6, the angle of the corner near the juncture of side surface 32 andbottom surface 28 shown before material was added to side surface 32 andbottom surface 28 (i.e. at outlet 20) (θ₁) is greater than the angle ofthe corner near the juncture of side surface 32 and bottom surface 28 atoutlet 20A (θ₂). Thus, the additional material added to the surfacesforms a sharper corner where side surface 32 and bottom surface 28 meet,reducing the chance of flow separation at that corner.

While FIG. 6 shows an embodiment in which all of the surfaces at outlet20A include additional material, additional material can be added to asfew as one of the surfaces in other embodiments.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A method for forming a diffusion cooling hole in a substrate can includeremoving material from the substrate to form a metering section havingan inlet on a first side of the substrate and removing material from thesubstrate to form a diffusing section that extends between the meteringsection and an outlet located on a second side of the substrategenerally opposite the first side. The method can also include forming afeature on a substrate surface within one of the metering section andthe diffusing section. Forming the feature can include depositing amaterial on the substrate surface and selectively heating the materialto join the material with the substrate surface and form the feature.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

A further embodiment of the foregoing method can include that the stepsof removing material from the substrate to form a metering section andremoving material from the substrate to form a diffusing section areperformed by a technique selected from the group consisting of casting,drilling, laser drilling, machining, electrical discharge machining andcombinations thereof.

A further embodiment of any of the foregoing methods can include thatthe substrate surface on which the feature is formed is located withinthe metering section.

A further embodiment of any of the foregoing methods can include thatthe feature obscures a line of sight between the inlet and the outlet.

A further embodiment of any of the foregoing methods can include thatthe feature obstructs a portion of the metering section to form acusp-like opening.

A further embodiment of any of the foregoing methods can include thatthe substrate surface on which the feature is formed is located withinthe diffusing section.

A further embodiment of any of the foregoing methods can include thatthe feature includes an apex and a plurality of planar sides extendingfrom the apex.

A further embodiment of any of the foregoing methods can include thatthe feature is formed along a surface of the substrate adjacent theoutlet.

A further embodiment of any of the foregoing methods can include thatthe outlet before forming the feature includes a corner having a firstangle, and wherein the feature forms a second corner having a secondangle generally smaller than the first angle.

A further embodiment of any of the foregoing methods can include thatthe feature is formed along substantially all of the substrate surfacesadjacent the outlet.

A further embodiment of any of the foregoing methods can include thatthe material deposited on the substrate surface is a metal.

A further embodiment of any of the foregoing methods can include thatthe material deposited on the substrate surface is a ceramic.

A further embodiment of any of the foregoing methods can include thatthe material deposited on the substrate surface is selectively heatedusing a laser.

A further embodiment of any of the foregoing methods can include thatthe material deposited on the substrate surface is selectively heatedusing an electron beam.

A further embodiment of any of the foregoing methods can include thatthe material is deposited on the substrate surface by spraying.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A gas turbine engine component comprising: a wall having a firstsurface and an opposing second surface; a diffusion cooling holeextending through the wall and fluidly connecting the first and secondwall surfaces, the diffusion cooling hole comprising: a metering sectionoriented along an axis and having an inner surface; and a diffusingsection adjacent to and downstream of the metering section; thediffusing section having a top surface and a bottom surface; and atleast one raised feature formed in the diffusion cooling hole, a portionof the at least one raised feature being proximate a transition pointbetween a downstream end of the metering section and an upstream end ofthe diffusing section.
 2. The component of claim 1 and furthercomprising: an inlet formed in the first wall surface upstream of themetering section.
 3. The component of claim 2 and further comprising: anoutlet formed in the second wall section downstream of the diffusingsection.
 4. The component of claim 3, wherein the raised feature isformed on the top surface of the diffusing section.
 5. The component ofclaim 4, wherein the at least one raised feature has a curved shape. 6.The component of claim 4, wherein the at least one raised featureobscures a line of sight between the inlet and the outlet.
 7. Thecomponent of claim 3, wherein the diffusing section further comprisesfirst and second opposing side surfaces extending between the topsurface and bottom surface.
 8. The component of claim 7, wherein thediffusing section bottom surface diverges longitudinally from the axis.9. The component of claim 8, wherein the at least one raised featurecomprises a first raised feature and a second raised feature.
 10. Thecomponent of claim 9, wherein the first raised feature is formed in themetering section, and the second raised feature is formed on at leastone of the top, bottom, or side surfaces of the diffusing section. 11.The component of claim 9, wherein the first and second raised featuresare formed from a technique selected from the group consisting ofselective laser melting, direct metal laser sintering, selective lasersintering, electron beam melting, and combinations thereof.
 12. Thecomponent of claim 3, wherein the diffusion cooling hole is formed by atechnique selected from the group consisting of casting, drilling, laserdrilling, machining, electrical discharge machining and combinationsthereof.
 13. The component of claim 3, wherein the wall is formedprimarily from a metallic material.
 14. The component of claim 3,wherein the gas turbine engine component is a vane, blade, combustor, orblade outer air seal.
 15. A gas turbine engine component comprising: awall having a first surface and an opposing second surface; a diffusioncooling hole extending through the wall and fluidly connecting the firstand second wall surfaces, the diffusion cooling hole comprising: ametering section oriented along an axis and having an inner surface; anda diffusing section adjacent to and downstream of the metering section;the diffusing section having a top surface and a bottom surface; and atleast one raised feature formed on the top surface of the diffusionsection.
 16. The component of claim 15, wherein the at least one raisedfeature has a curved shape.
 17. The component of claim 15, wherein theraised feature is formed from a technique selected from the groupconsisting of selective laser melting, direct metal laser sintering,selective laser sintering, electron beam melting, and combinationsthereof.
 18. The component of claim 15, wherein the diffusion coolinghole is formed by a technique selected from the group consisting ofcasting, drilling, laser drilling, machining, electrical dischargemachining and combinations thereof.
 19. The component of claim 15,wherein the diffusing section further comprises first and secondopposing side surfaces extending between the top surface and bottomsurface.
 20. The component of claim 19, wherein the raised feature isfurther formed on the side and bottom surfaces.